The Photosphere and Wien's Law

The temperatures of the photosphere displayed in the table of the adjacent panel come from a detailed analysis of the Sun's atmosphere. However, we can deduce immediately that the average temperature must lie in this range by the following argument.

The Sun emits light that has maximum intensity in the yellow region of the spectrum at about 5100 Angstroms. Inserting that into Wien's Law for blackbody radiators (see this Java applet), we conclude that the dominant light from the Sun is being emitted from a region in the surface at a temperature of about 5700 K.